Induction motor



May 6, 1924. I $393,184 E. C. BALLMAN I INDUCT I ON. MOTOR;

Fild Jan. 19. 1920 W/y C 5A 1.1. MAN) i Motors.

Patented May 6, 1924.

EDWIN c. BALLMAN, ors'r. LO'UIS, Mrssoum;

IIIDUCTION MOTOR.

Application-filed January 19, 1920. Serial ua asassa To all whom it. may concern:

Be it known that I, EDWIN C. BALL'MAN, a citizen of the United States, and residing at St Louis, Missouri, have, invented the new and-useful Improvement in Induction I of which the following is a specification.

This invention relates to electric motors, and more particularly'to alternating current commutator motors. I

There are a number of types of commutator motors at present in use, whose operating characteristics require that the commutator'beshort circuited after the motor has attained a predetermined speed. The

. means for' effecting such short circuit usually take the form of a series of contactors arranged tov make contact with an inner cylindrical surface of the commutator. The arrangements for making and breaking contact are usually such asto produce arcing at the point of making orbreaking con- "tact. This has the effect of burning or corroding the contact surfaces. This results in 'rougheningthose surfaces, and as the contacts are usually arranged to slide into and outbf engagement, the rough surfaces cause sticking, action. I

One of the objects of this-invention, there fore, is to provide improved means for short circuiting the commutator which shall 0bviate burning and corrosion of the contact surfaces.

' the surface.

.Another difiiculty encountered with the usual construction is that the inner cylindrical contact surface of the commutator is so located as to be inaccessible for cleaning .Another object of this invention, there fore, is to provide short circuiting means.

Figure 3. is an enlarged detail view of the short circuiting conductor. and one of the contactors, said contactors being shown in the position assumed at the instant of making or breaking contact; and

Figure 4 is a view similar to Figure 3 and consequently, uncertainty of showing the contactor in the position assumed while maintaining the short circuit.

Referring now to the drawing, 1 designates the stator, and 2 the rotor of an alternating current commutator motor. This rotor has a winding 3 connected to a com mutator 4 carried by a commutator'support 5. These parts may be of any usual and well known construction and no. further description thereof is needed, with the exception that the-commutator 4 is provided with a more or lessexte'nded radial face 6 adapted to engage a series of contactors 7'. The

-face 6 is preferably located on the front of the commutator so as to be accessible for cleaning without dismantling the motor.

Mounted on the shaft 8 of the motor is a support 9 adapted to slide on said shaft. The support 9 is provided with an annular recess 10 adapted to accommodate a helical spring 11 bearing at one end against the bottom of the recess 10 and at the other end against the commutator support 5. The support '9 is internally threaded to receive the ends of tension rods 12 extending rearwardly therefrom and passing through open- .ings 13 in the commutator support, and

similar 0penings'14 in the body of the rotor. The rearward end of each rod 12 is pivotally connected at 15 with one arm of a bell crank. .16 pivoted at 17 on-the rotor body, the other arm of the bell crank being provided with a weight 18. Thewcights 18 are forced radially. outward by centrifugal force whenthe motor runs, and are adapted through the agency of the bell cranks 16'and the rods 12.to move the support 9 rearwardly,

when such speed is attained that the cen- .-trifugal force of the weights 18 is sufiicient to overcome the tension of the spring 11. The support 9 is provided with an abutment 19 adapted, by engagement with the shoulder 20 on the shaft 8, to limit the rearward movement of said support.

Mounted on the support 9' is a short circuiting conductor 21 of copper, brass or other suitable conducting material. This conductor has the shape of a flat ring and may be attached to the support 9-by being fitted into'an annular recess 22 and spinning over the outer rim of said recess to hold said ring in place or by other suitable means.

The support 9 is further provided with an annular recess 23 adapted to form an annular chamber partially closed by' the a deep recess, the bottom of which forms aconductor 21. The inner Wall of the recess 23 takes theform of a barrel extending rearwardly to a point opposite the conductor 21, so as to form a restricted opening 24 for the annular chamber, in which a plurality of contactors 7 areassemb1ed.

Each contactor is provided at one extremity with an enlarged portion 25 at its otherextremity with a pair of contact faces 26 and 27. Intermediate the extremities. is

pivot portion 28 adapted for engagement with the innerjedgeof the conductor 21.

These contactors are assembled upon the ring 21 by insertingsaid ring into the recess up to the pivot portion 28. A sufficient number of these contactors is so asi' sembled to entirely'fill up the ring,.suflicient looseness being permitted to insure free and unrestricted movement of the contactors. When all of the contactors'havebeen assembled upon "the conductor- 21, said conductor is assembled uponthe support 9 and fixed theretoas previously described. It will be understood that when all the contactors are thus assembled, each will be held in radial position by its neighbors and, the opening 2a being too'sma-ll to allow the enlarged portion 25 to pass therethrough, the contactors will be permanently assembled on the conductor 21, but will be sufficiently loose to insure free-and unrestricted movement about the pivot portion 28.

- centrifugal force of rotation acting on the ,contactors 7 will force them against the conductor 21 at the pivoted point 28 and. will, therefore, insure good contact with said conductor. The contactors 7,- by making contact with the individual barsof the commutator 4 and with the conductor 21,

Will short/circuit said commutator. a

The action of centrifugal forceupon the contactors 7 will, when their movement is unrestricted, cause said 'contactor's to assume a position with reference-to the conductor 21 as shown in Figure 3. This is due to the fact that the weight of the enlarged portion 25. is greater than that of the opposite extremity of the contactor and, its

centrifugal force being greater, the contactor will turn about the pivoted portion 28 in aclockwise direction until stopped by engagement of the portion with the conductor 21. This position will be assumed by all of the contactors as soon as the motor When starting the of the support 9, the contactors 7 will rotate about the pivot portion 28, thecontact face 26 sliding outwardly and the contact face 27 laterally coming into engagement with the commutator. The contact faces 26 and 27 are spaced from oneanother asuificient distance to insure that the face 27 will engage the commutator at a diflerent point than that of the face 26. Upon completion .of the movement of the su port 9, the

contactors will make the position shown in Figure withthe contact face 27 firmly in engagement with the commutator, the portion 25 moved out of engagement with the conductor 21 so that centrifugal forceacting on said portion 25 will have the effect of exertingv contact pressure both at the pivoted portion 28 and at the face 27. The commutator is, therefore, definitely and 'positively short'circuited.

The support 9 may also be provided with a loose ring 29 adapted upon movement of the support 9 to engage a member 30 on the brush holder to lift the brushes 31 from the commutator.

Upon stopping the motor, the reverse of the above described operations will take place. \Vhen the rotor has fallen off sufficiently in speed. the spring 11, overcoming the centrifugal force of the Weights 18, will move the support 9.forwardly.' Upon such movement, the contactor 7, being still acted upon by centrifugal 'force, as the motor has not yet come to rest, will rotate in a clockwise direction, 3) the contact face 27 sliding radially inwardly until the contact face 26 engages with thecommutator, whereuponfurther movement will disengage the face 27, leaving the'face 26 in contact. Still further movement will disengage the face.26, and it -willbe seen that whatever arcing takes place upon breaking the circuit will again takeplace at the face'26. It will be'seen, therefore, that all thearcing upon making and breaking the circuit wil take place at the face 26 and all burning and corrosion will be confined to said face and to its point of engagement with the commutator, leaving tl'e face 27 and its pointof engagement perfectly clean and in the best condition to insure a perfect contact.

It will be seen. therefore, that this invention accomplishes its stated ob ects 1n providing a short circuiting device in which and described.

the troubles due to burning and corrosion at the contact points are eliminated and the contact surfaces are rendered accessible for cleaning.

. It is obvious that various changes may Having thus described 'this invention, what is claimed is: A

1. In an alternating current motor having a commutator, means for short-circuiting said commutator, including a contactor having a contact face, a weight, and a pivot portion intermediate said contact face-and said weight, adapted bycentrifugal force to 'move said contactor to contacting position.

2. In' an alternating current motor having' a commutator, means for short-circuit ing said commutator, including a contactor having a contact face, adapted to butt against the'commutator, a -weight, and a pivot portion intermediate said contact face and said Weight, adapted by centrifugal 1 force to apply contacting pressure at and I0 to said contact face.

3. In an alternating current motor hav ing a commutator. provided with a radial face, means for short-circuiting said commutator,including a contactor havingja erable number of segments, means for shortcircuiting said commutator comprising, a

contact ,face adapted to butt against the radial face of the commutator, a weight, anda pivot portion intermediate said contact face and said weight, adapted by centrifsaid commutator face. a

4. In an alternating current motor having a commutator, means for short-circuiting said commutator, including'a contactor having a contact face, a Weight and a pivot portion intermediate 'said contact face arid said Weight, adapted by centrifugal force to apply contacting pressure both at said contact face and at said pivot portion, said, commutator being adapted to en age said contact face, and acohductor a apt'ed to engage said pivot portion.

5. In an alternating current motor provided with a commutator having a considseries of contactors, an annular pivot adapted. to support said cont-actors in adjacent annular relation so'as to engage the commutator segments, each contactor having a weight portion, a lever portion. and a contact face, adapted by centrifugal force of said weight to apply contacting pres-' sure to said contact face, through said lever portion.

'6. In an alternating currentf motor havinga commutator, means for short-circuiting said commutator, including, a contactor having two contact faces adapted to'engage said commutator, constructed and arranged so that one of said faces will engage before, and disengage after the engagement or disengagement respectively of said other face.

7. In an alternating. current motor having a commutator, means for short-circuiting said commutator, including, a contactor having two contact faces adapted to engage'said commutator, constructed and arranged so that one of said faces-will engage at a different point on said commutator from said other face.

-8.' In an alternating current motor having a commutator, means for short-circuit ing said commutator, adapted to engage said commutator for making and breaking the circuit at one point on said means, and for maintaining the circuit at another point thereon spaced from said first point.

- 9. In an alternating current motor having a commutator, means for short-circuiting said commutator, comprising, a plurality of contactors each having a notch, 21 short-circuiting conductor engaging said notches, whereby said contactors maybe assembled on said conductor, and a'supporting memberfor said conductor having a part positioned opposite the contactor-engaging portion thereof adapted to maintain said contactors i'n assembled relation thereon.

10. In an alternating current motor having a commutator, means for short-circuiting said commutator, comprising, a pluralugal force to apply contacting pressure to' ity of contactors each having a deep recess, a short-circuiting conductor engaging said recesses, whereby said contactors may be assembled on said conductor, and a supporting member for said conductor having a part positioned to prevent disengagement of said recesses; from said conductor, adapted to maintain said contactors in assembled; relation on said conductor.-

11. In an alternating current motor hav-,

inga commutator, means for short-circuit- I- ing said commutator, comprising, a short circuitin conductor, a contactor having a recess a apted to' engage said conductor whereby said contact-or may be assembled thereon, and a supporting member for said conductor, adapted to prevent disengagement of said contactor from-said conductor.

12. In an alternating current motor having a: commutator, a contactor having a making and breaking contact and a circuit maintaining contact.

Intestimony whereof I afiix my signature this 19th day of December, 1919.

EDWIN o. BALLMAN. 

